Cub Stopped Running

[Peter Person]

Looking for confirmation or other possibilities as to why my 1957 Cub ran fine, died, ran fine this morning plowing the 3" of heavy wet snow we got.
I'm suspecting either the needle stuck for a few minutes or a piece of debris was blocking something. The carb last had a thorough cleaning 6-8 years ago.
Coil was cool to the touch.

I was plowing for about 15 minutes when it just quit running. Tried restarting but no luck. Let it set for about 5 minutes and it started right up without any choke. Ran fine for another 2 hours.

Thanks,
Peter

[Slim140]

I'm guessing the float got stuck or you had a blockage of fuel that passed. Look in the tank and make sure nothing is on the bottom swimming around that could cover the hole.

[ntrenn]

My 65 did something similar...a light shot of air backwards through the fuel line dislodged whatever was restricting the fuel. Been good for the last 2 weekends of leaf mowing.

[Lt.Mike]

Icing?

[lowgearfarm]

I concur with the "icing" guess. My '49 was doing the same thing last week ie: running fine, then sudden shut-down suggesting "out of fuel", then started up and ran fine. Repeated 3 or 4 times in an hour. Air temp was 17F, suspicious signs of frost around the gas line shut-off valve. Note: I was running aviation fuel that had been in the tank for 3 months. I topped up the tank before putting it away.
Yesterday, I went out plowing again, temp at 29F, fully expected a stalling or two, but never happened! (Life is good - sometimes) Now I'm wondering if I should try a little "dry gas" in the aviation fuel (for the Cub only). I buy the aviation fuel for the little engines (chainsaws, splitter, etc.) that sit for months.

[Peter Person]

Thanks for all the input.
Just finished plowing 10" of 3-5" of additional accumulation
No issues today at all, other than I still need to put my chains on.

I don't think it was icing as temps were in the 28-36 degree range.
I'll go with something in the fuel that blocked a jet or caused the needle to stick.

Peter

[tnestell]

Thanks for all the input.


I don't think it was icing as temps were in the 28-36 degree range.


Peter

Carb icing can occur at temps higher than 36 degrees. Incoming air is compressed going through the venturi producing heat and then expanding causing it to cool, along with gas vaporizing causing more chilling. So on a humid day, temp about 35, moisture in the air condenses and can cause frost and blocking incoming air.

[Crimson Tim]

Carb icing can occur at temps higher than 36 degrees. Incoming air is compressed going through the venturi producing heat and then expanding causing it to cool, along with gas vaporizing causing more chilling. So on a humid day, temp about 35, moisture in the air condenses can and can cause frost and blocking incoming air.

I wondered about this possibility, too.
On hot, humid days, I’ve seen how the carb can get cold enough to condense water out of the air. If the carb can be 20-30 degrees cooler than ambient when it’s 95 outside, it seems reasonable it might be 5-10 degrees cooler when it’s 35. Could be enough to freeze up any moisture in the incoming fuel or air.

[Waif]

I was surprised once after taking a visual of a main jet before running a wire in it on a winter fuel starvation...It looked clear.
And when wired , a broken rim/rind of ice came out. Thought it was varnish at first ,till it faded quickly in my fingers....L.o.l..

[lowgearfarm]

Been plowing snow for the past few days. The air has been moist and the temps around freezing. The '49 Cub (w/ IH carb) runs fine until it quits - presumably from icing. Put a hair dryer to the carb and that brought the engine back to life for the rest of the morning. For a while I assumed the problem was gas line freeze (see photo) and planned to add dry gas to the aviation fuel. But then I wondered if the carb freezing it might be from the air intake. I'm reminded of auto engine ducts that take hot air from outside the exhaust manifold and channel the warm air to the air cleaner to mix with outside air. But before I add dry gas or try to rig-up a hot air duct, I wonder if this group had opinion as to 1) whether the icing is fuel or air related (or both), and 2) whether there are any home-grown fixes I haven't thought of? And 3) why moisture is icing around the joint of the fuel shut-off? Thanks.
~Ned

[Don McCombs]

The Cub's primitive crankcase ventilation system moves fumes from the crankcase to the air cleaner by way of a steel tube attached to both. The tube gets obstructed by combustion products over time. It is possible that clearing that tube and it's adjacent fittings may solve your problem. Don't have an explanation for the icing on the fuel shutoff.

[lowgearfarm]

Don, Thanks for your suggestion. I wasn't aware of the crankcase vent tube. I'll go take it off after lunch and clean as necessary - assuming I don't have to lift the hood or split the tractor to get at it
~Ned

[Don McCombs]

You can try, but that may be an issue.

[indy61]

why moisture is icing around the joint of the fuel shut-off? Thanks.
~Ned

I would guess the little plastic shut off valve is sucking air at high rpm's. It probably leaks but evaporates faster than you can notice.

[BigBill]

My first 154 did that it would stall, wait five minutes she’d fire up and finish mowing, after a few times she finally wouldn’t start, I pulled the hose off the carb to find no gas flow, even with the valve on no gas. I opened the gas cap and blew into the fuel hose as hard as I could, I heard a big pop in the gas tank. There was a clog above the fuel valve assembly. She’s been running ever since. It’s a 154 but we all have the same fuel valves.

After being a car mechanic and working in gas stations and dealerships the people let the level of gas go low in the wintertime. This causes moisture to form more in the gas tanks. The weather change from warmer to colder causes moisture to form. Day by day our temps change. I tell everyone to top off there gas tanks and add gas line anti freeze in the winter time. Years ago we had a lot of people with frozen gas lines.

Note, never buy gas when the delivery truck is there dropping off gas. It stirs up the water in the bottom of the tank. We stick the tanks for water before the drop. A small amount is allowed. But the drop can stir up what little there is.

My equipment gets seafoam and a little dry gas..